How to move layers around?
There's no direct way to move layers around from the UI.  I think the best you can do is select the source layer (either clicking in the properties panel or using the ShiftM popup), use A to select all bones, and then M-ove them to the destination layer, assuming the destination layer is empty.  If you are trying to swap two layers &quot;X&quot; and &quot;Y&quot;, you need to move all the bones in &quot;X&quot; to a spare empty layer &quot;Z&quot;, then move &quot;Y&quot; to &quot;X&quot;, and them move &quot;Z&quot; to &quot;Y&quot;.